Allow override gradle version for plugin tests

tools/kotlin-native-gradle-plugin/build.gradle

@@ -191,6 +191,9 @@ test {
     if (project.hasProperty("filter")) {
         filter.includeTestsMatching project.property("filter")
     }
+    if (project.hasProperty("gradleVersion")) {
+        systemProperty("gradleVersion", project.property("gradleVersion"))
+    }
 }
 
 processResources {

tools/kotlin-native-gradle-plugin/src/test/groovy/org/jetbrains/kotlin/gradle/plugin/test/KonanProject.groovy

@@ -17,6 +17,7 @@
 package org.jetbrains.kotlin.gradle.plugin.test
 
 import org.gradle.testkit.runner.GradleRunner
+import org.gradle.util.GradleVersion
 import org.jetbrains.kotlin.konan.target.HostManager
 
 import java.nio.file.Files
@@ -49,6 +50,7 @@ class KonanProject {
     File konanBuildDir
 
     String konanHome
+    String gradleVersion
 
     File         buildFile
     File         propertiesFile
@@ -95,10 +97,15 @@ class KonanProject {
         }
         // Escape windows path separator
         this.konanHome = escapeBackSlashes(konanHomeDir.canonicalPath)
+        this.gradleVersion = System.getProperty("gradleVersion") ?: GradleVersion.current().version
     }
 
     GradleRunner createRunner(boolean withDebug = true) {
-        return GradleRunner.create().withProjectDir(projectDir).withPluginClasspath().withDebug(withDebug)
+        return GradleRunner.create()
+                .withProjectDir(projectDir)
+                .withPluginClasspath()
+                .withDebug(withDebug)
+                .withGradleVersion(gradleVersion)
     }
 
     /** Creates a subdirectory specified by the given path. */